I guess in an ideal world, a service like this would be a layer on top of Terraform. Changes in the admin page would be applied using Terraform, and update the config in your own Git repository. I think this would be much easier to sell, even if they choose to make it "write only" to avoid potential complexity of managing user defined configs.

They could get customers initially by promising a simple start to get "on the cloud", but would keep customers due to support, scaling, monitoring, ci/cd and maintenance. Cheap startups could use it as a one-time tool, but I think a lot would see the added value they bring.